This symposium, to be convened immediately preceding the annual meetings of The Society for Epidemiologic Research in Buffalo, NY, in 1991, will be held to honor Dr. Saxon Graham at the occasion of his retirement. The goal of the symposium is to bring together some of the most innovative researchers in the area of diet and cancer. These scientists, specialists in epidemiology, statistics, nutrition and policy, have been invited to evaluate past research and discuss creative new directions for the field. Epidemiologic research on diet and cancer has grown geometrically in the past two decades, and a comprehensive assessment of progress to date, with a thoughtful speculation as to the future, would serve the field well at this time. For this symposium we will focus on two of the more common sites of cancer, the breast and the large bowel. Both have been the subject of several investigations regarding the etiologic involvement of diet. Although these two sites will be the focus of discussions, ideas presented will also be of relevance to study of other sites. The symposium will also address methodologic issues; Measurement and causal inference remain central foci of nutritional epidemiology, open to much further study. Finally, the symposium will address policy concerns and the degree to which, at this point in our research, it is appropriate to issue recommendations for disease prevention.